Sulfur combined

Silver and sulfur combine even in the cold to form silver sulfide. The tendency of silver to tarnish is an example of the ease with which silver and sulfur compounds react. PoHshes that contain silver complexing agents, such as chloride ion or thiourea, are used to remove silver tarnish. 

Sulfur combines direcdy and usually energetically with almost all of the elements. Exceptions include gold, platinum, iridium, and the hehum-group gases (19). In the presence of oxygen or dry air, sulfur is very slowly oxidized to sulfur dioxide. When burned in air, it forms predominantly sulfur dioxide with small amounts of sulfur trioxide. When burned in the presence of moist air, sulfurous acid and sulfuric acids are slowly generated. 

Sulfur combines directly with hydrogen at 150—200°C to form hydrogen sulfide. Molten sulfur reacts with hydrogen to form hydrogen polysulfides. At red heat, sulfur and carbon unite to form carbon disulfide. This is a commercially important reaction in Europe, although natural gas is used to produce carbon disulfide in the United States. In aqueous solutions of alkaU carbonates and alkaU and alkaline-earth hydroxides, sulfur reacts to form sulfides, polysulfides, thiosulfates, and sulfites. 

Furthermore, sulfur combines with copper rather than with iron. Hence, copper sulfide remains ia the converter after the iron has been oxidized and has combiaed with siUca to be skimmed off as a slag. Typical converting reactions of iron sulfide are equations 11, 14, and 15. 

Finally, sulfur occurs in many localities as the sulfates of electropositive elements (see Chapters 4 and 5) and to a lesser extent as sulfates of Al, Fe, Cu and Pb, etc. Gypsum (CaS04.2H20) and anhydrite (CaSO ) are particularly notable but are little used as a source of sulfur because of high capital and operating costs. Similarly, by far the largest untapped source of sulfur is in the oceans as the dissolved sulfates of Mg, Ca and K. It has been estimated that there are some 1.5 x 10 cubic km of water in the oceans of the world and that 1 cubic km of sea-water contains approximately 1 million tonnes of sulfur combined as sulfate. 

I.5.2.2.3.2.3. Asymmetric Induction from the Stereocenter at Sulfur Combined with Simple... 

F.10 A chemist found that 4.69 g of sulfur combined with fluorine to produce 15.81 g of a gas. (a) What is the empirical formula of the gas (b) Assuming that the empirical and molecular formulas of the compound are the same, what is its name ... 

Table 11.19 gives the cure characteristics of the blends for high and low peroxide, sulfur, and co-agent (peroxide + sulfur) combinations. They found that the maximum and minimum torques... 

Another key feature of sulfur chemistry is the Lewis acidity of sulfur dioxide. Sulfur dioxide is a common atmospheric pollutant that results from burning coal to produce electricity. Most coal reserves in North America include significant amounts of sulfur-containing impurities. When coal is burned, sulfur combines with O2 to form SO2, a hard Lewis acid. 

Bismuth reacts with chlorine, bromine and iodine vapors forming chloride, bromide and iodide of the metal, respectively. Molten bismuth and sulfur combine to form bismuth sulfide, Bi2S3. 

Conventional cure systems use relatively high levels (2.5 + phr) of sulfur combined with lower levels of accelerators). These typically provide high initial physical properties, tensile and tear strengths, and good initial fatigue life, but with a greater tendency to lose these properties after heat aging. 

However, it was the availability of large quantities of byproduct sulfur combined with the energy crisis of the early 1970 s which stimulated the research and development needed to make sulfur-asphalt technology a commercial reality. The need to dispose of large potential tonnages of sulfur and the need to find alternative new materials to increasingly expensive petroleum-based asphalt spurred interest and research by many organizations. 

Figure 8.6 Effect of temperature on rate of sulfur combination.

Three sulfur forms recognized by ASTM are tl) sulfate sulfur, which may be in the form of calcium or iron sulfate (2) pyritic sulfur, which is sulfur combined with iron in the form of minerals pyrite and/or mareasiic and (3) organic sulfur, which is bonded to the carbon structure. 

Thorium sulfide, ThSz, is obtained by the action of H2S or sulfur on thonum metal. The oxysulfide, ThOS. has been obtained in several ways, one of which is by the action of CS2 on thorium dioxide at elevated temperatures. At 800°C and under pressure, sulfur combines with thonum to yield compounds with approximately die formulas ThS, TI12S3, and TI13S7 The first two have semimetallic properties and may be employed as ceramics for use with highly electropositive metals, whereas the last appears to be a poly sulfide. 

Vicinal syn- and aufi-diols, as shown in Figure 4.42, can be prepared diastereoselectively (cf. Figures 8.10,8.13-8.15,8.32). In the Corey-Winter process they are first converted into cyclic thiocarbonates (cf. Section 6.4.4 for a similar reaction mechanism). Upon heating in trimethyl phosphite, these thiocarbonates furnish olefins. In what is evidently a one-step reaction, phosphorus and sulfur combine with one another and the five-membered heterocycle fragments. C02 is released and the olefin results from a xyu-elimination. Because of the latter, a syu-diol gives the trans-oieim and an anti- diol gives the cw-olefin in the Corey-Winter sequence. 

The strategies used in studies of high temperature reactions of metals have been brought to bear on some of the problems associated with the direct liquefaction of coaL Many coals contain sulfur, combined in both organic and inorganic forms, in excess of amounts allowable under current combustion standards. In some coals much of the sulfur is in the form of pyrite, Fe 2> which may, paradoxically, serve as a catalyst or the precursor of a catalyst for the liquefaction process. The information available for the Fe-S-O-H system has been assembled in an attempt to provide a framework for interpreting experimental results, and to facilitate the planning of further experim ents. 

Potassium Chlorate is a highly unstable and dangerous compound when used in a pyro-technical mixture which also contains sulfur. Combined, these two compounds are sensitive to both heat and friction as well as sparks, and are made more so by moisture absorbed from the humidity in the air. Furthermore, they deteriorate on storage slowly producing sulfuric acid which makes the mixture even more unstable. 

Hydrogenolysis of compounds with sulfur atoms attached to aromatic rings such as benzenethiols, and aryl sulfides, disulfides, sulfoxides and sulfones takes place on refluxing with Raney nickel or nickel boride. Sulfur combines with nickel, and hydrogen replaces the sulfur-containing group. 

The elements silver, molybdenum, and sulfur combine to form Ag2MoS4. What is the maximum mass of Ag2MoS4 that can be obtained if 8.63 g of silver, 3.36 g of molybdenum, and 4.81 g of sulfur are combined ... 

Buna 85 is polybutadiene (the number represents Mooney viscosity), molecular weight -80,000. Hard rubber has high softening point and excellent chemical resistance. The coefficient of vulcanisation to the ebonite stage is 39.3. The coefficient of vulcanisation is the number of unit weight of sulfur combined with 100 units by weight of unsaturated hydrocarbons. Buna S is a butadiene styrene copolymer with 70/30 to 68/32 ratio. Buna SS contains a high proportion of styrene. Perbunan are nitrile rubbers... 

Hard rubber or ebonite whether from natural rubber or from synthetic rubber, can be defined as highly vulcanised rubber, containing a large proportion of combined sulfur. Hard rubbers made from natural rubber have vulcanisation coefficients between 25 and 47. The theoretical vulcanisation coefficient value for natural rubber is 47 and for synthetic rubbers it is in the range of 35 to 47. The coefficient of vulcanisation is usually defined as the number of units by weight of sulfur combined with 100 units by weight of unsaturated hydrocarbon. The theoretical coefficients are corrected for impurities/non rubber constituents in the raw rubber. 

Sulfur combines with platinum sponge or the finely divided metal on ignition and forms PtS. The same product is also produced when hydrogen sulfide is passed into a solution of an alkali chlorplatinite. 

Relation to Sulfurous Acid.—Sulfurous acid is an antiseptic, mild or strong, according to the quantities used. The fumes of burning sulfur are used in various ways and for various purposes in wine-making. The active principle of these fumes is sulfurous acid gas of which the chemical formula S02 shows that it is composed of one. atom of sulfur combined with two atoms of... 

Resistant strains of P. acnes are emerging that may respond to jndicions nse of retinoids in combination with antibiotics. Commonly nsed topical antimicrobials in acne inclnde erythromycin, clindamycin (Cleocin-t), and benzoyl peroxide and antibiotic-benzoyl peroxide combinations (Benzamycin, Benzaclin, others). Other antimiaobials nsed in treating acne inclnde sulfacetamide (Klaron), sulfacetamide/sulfur combinations (Snlfacet-R), metronidawie (Metrocream, Metro-Gel, noritate), and azelaic acid (Azelex). Systemic therapy is prescribed for patients with more extensive disease and acne that is resistant to topical therapy. Effective agents inclnde tetracycline (snmycin, others), minocycline (MINO-CIN, others), erythromycin (ERYC, others), clindamycin (CLEOCIN), and trimethoprim-sulfamethoxazole (bactrim, others). Antibiotics nsnally are administered twice daily, and doses are tapered after control is achieved. 

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